Method of producing a low density explosive



Oct. 23, 1956 H. J. STARK METHOD oF PRoDUcING A Low DENSITY ExPLosIvEFiled Aug. 15, 1955 5 Sheets-Sheet 1 MM LV m0 ZOFDJOm l INVENToR. )'14HOMIRD J. STA/'7K ZA TTORNE'Y w Oct. 23, 1956 H. J. STARK 2,763,072

'- METHOD oF PRonucING A Low DENSITY EXPLosIvE 3 Sheets-Sheet 2 WARHEDFOAMED EXPLOSIVE 74/72 im ENGINE l HIGH EXPLOSIVE 70 FIG. 7.

1N VEN TOR. How/mo .1. sun/r BY Z fig@ f A T TOR/VE Y Oct. 23, 1956 H.J. STARK METHOD oF PRoDUcING A Low DENSITY ExPLosIvE Filed Aug. 15,-1955 5 Sheets-Sheet 3 FIG. 9.

FOAMED EXPLDSIVE INVENTOR. HOMRD J S TARK Z ATTNEY United States PatentAME'IFI-IODT OF IPRODUCIN G .iA-'.:ILOWfDEN-SITY :EXBLOSIVE Theinvent-ion -described herein 'ma-y ibe :manufactured and use'd Abyorffori'theGovernmentof thefUnitedStates -of America for fgovermentlpurposes `Withoutlthe fpayfm'ent'4 o'f v any1 royalties Jthereon: ortherefor.

This invention relates to low density explosives andfin particular tothe process ofmanufacturing -a-low'density, cellular explosive foam.

Thisis ajcontinuation-in-:par't applicationo'f copending applicationSerial No. 300,367, `tiled June 30, 1952, and lentitled VMeth-od -ofProducing a vLow -Densit-y 'Explosive which was a divisional applicationof Serial No. 185,900, filed September 20, 1950,. andrentitledLowiDensity- Gelhl- `lar Explosive Foam .both of=whichrapplications are now abandoned.

The general object of the invention is -to fprovide an .explosive havinga cellular foam structure whichbecause 'of such foam structure, is ofrelatively`low-;lensity,is '.buoyant with respect to water, andof'greaterr-and more rapid shattering eiect'than thesame weighto'fliighdensity explosive.

It is also an object ofthezinventionto provide Van ex- .plosivehaving.acellulanoamstructure which is set and rigid Y,and .which is`relatively=strong.and r tough,

.-Ittis a further object of the v4inventiion Y.to ,providaan explosivehaving ar-cellularifoam structure whichlnayhe .castior molded zinto laparticular. shapetpiior. tothe setting or assumption of rigidity. v A

.Other :objectives -will tbe..apparent1from ,the .followingIdescriptionand fromrthedrawingsrhereto attached, fwhichare,illustrative\of .the method `of .making `the cellula'rrexplosive and.of-` the preferred .embodimentsoflhel invention.

.In these drawings Fig. 1 ,is .allowrchart .of the `dynamic`air-setmethod Yof .this invention; Y

Fig. 2 is a llow chart ,of the chemicalblowinmethod of this invention;

Fig. 3 is a diagrammatic transverse ,section through La conventionalfloating mine;

Fig. 4 is a diagrammatic transverse .sectiontthrough ia floatingmine .ofthe '.typeillustrated .bysEig but containinga relatively. large=quantityro'f.theifoametl explosive `of -this `invention {..cast linsitu;

Fig.,5.=is ,a diagrammatic sectionalzelevational view-.of aoatingmine`in Ywhich ihershelllis -,.coinprise'd of the molded foamed vexplosive.of this 'invention encased `in .light weight metal.onimpregnatedfabric.and shows-.fthe increased` highexplosive 'charge rpossible @with this,typeof construction;

.-.Fig..6 is .a.diagramma'ticlongitudinal:section 'through .a.'loating,:harbor Amine showing .the .combination in ,the explosivechargetothe.conventionallliigh ddensity explosive with the'foamedexplosive ofthis'invention;

1"Fig, T7 `'is aAdi-agrarnmat-ic longitudinal =sectionleleva tional Viewof a torpedo carrying a charge of high/density exp lesive andifoamedrexplosivetoffthisi invention; Land Figs. 8 and 9 are adiagrammaticflongitudinalssectionalelevationalsview;:anda.-transversefsectionalViewtakenfonline 9-9 of Fig. 8, respectively,totfafradioteontrolied 7 given Volume.

"ice

2 homing vessel 'showing the lfoametlexplosive of this`mventionfcast:and molded'within tthe'structure of the double walledfhull. l

Heretofore, l`it; `hasbeen'the-practice,in the manufacture ofexplosives, 'topro'duce lthem with a relatively high density in-ordertto have -a great explosive effect in a i' Now -fa 4requirement Vhasarisen in which nitisdesirable tohave'ean'explosive which is buoyant and`which may 4have a Jgreater explosive `effect which `may beaiditiveltothat ofrtheeonventional high `"density explosive. 'This requirement"ispresentnot only in rfloating mine -structures, but -also in wrtheguided surface (the -so-callefl homing) vessels. i'

Il-iis inventorhas met this `requirement by providing a vfoarntypeexplosive vvliii'zhfesem'bles "in5phy'sical ap- -pearanceand-.characteristics cellular polystyreneforcellu- .larA acetate. It-isrc'el'ativestrong andtough anlthe'density thereofcan "be varied byformulation within the range \of-`from"bout 5 -to about "501pounls perIcubictfoot.

'Thecellsefltheifoamed -andfset structure of vthe-ex- =plosiveraresubstantiallynon-communicating and referred to as closed-cells incontradistinctionlto spongy open-cells. rTherefore, aunlde'dplatedfithis material-iisfrelativlyimpervious to Agas `and awater. 'Incomparison with blsa rwooLvi/hieh hasfafbuoyancyof abouttwentylpoundsper cubic foot after twentfwfour hours `immersion under -a Vten ffoothead Lof '-water, this 'cellular explosive has e. ibu'oy-ancy offrom-aboutZO to about 50pounds per 'cubic foot under similar conditions.

The Efollowing fexplosives, as -well x-as others, can fbepreparedinfoamv'orlcellularform: `r(.1) lrinitrotoluene (2-)y,Nitnocellulose (tri, ,hexa ,and rdodelta. nitrocellulose) (3,)Rentaerythritl Y f (4) RDX l(cyclo .trimethylenetrinitramine)Thefoamedeexplosive rconsists essentially of vanyJone-of -theabove-.explosives ^bondedfby Va ffoaming. plastic.

A 'foaming plastic is :a `plastic Iwhich-will 'be of solid cellularstructure when fit is allowed to ysetrafterbeing foamed either bychemically or mechanically blowing gas or :lair through it iwhjle in theliquid `stagems will rappearinthe -examplessset'forth belo '.'This.inventor :has rfound `that :polyesters .of :ethylene:glycolr-maleic:anhydride intermixed \with :monomeric :styrene isideally suitedlasi afresininfthe carryingaouty ofithis iinvention.VThis:resinziszshown and described salong'with :other resins wvhich alsoare suitable .in Carleton .Elliss f-Pa-tent;2',255,3'13,which isincorporated byi reference and forrns :a 4apart :ofithisrfspecilc-ation; Of :course .a ller .as used in :the examples :ofEllisfs unnecessaryand not `used -althoughisuchusewould stillffallwitliinithefscope: of what is considered to bethe @present invention.

An example` 'offone of these fresins is 'that'.pro'duced@ by fheating5.00 partsof maleic anhydride. and 541gparts'diethyleneglycolineanoillbath at.220-.22`5 C. vfor'7 hours 'awhile bubblingnitrogen igas therethrough to provide i an inert atmosphere.The.diethylene.g'lycol maleateiformell =is a Ilight-colore'd iviscous:liquid `of acid :number 7.1. .Eighty-five .tparts Lof. this :liquid:arernilxed with 5 parts 'monomericistyrenet in -fa glasszeontainer.with a mechanically isdriven :stirren The iresultant :liquid 'is 1asatisfactory -stocka solution andrhas 35% tttbyzweight) benzolrpernxide('curing agent) uand 1/2;% 1.(.by weight) cobalt'naphthanate.(aceeleratoryfaddedto it iustzprionto: itsuse.

These bonding thermosetting polyester resinslarefwell known in theLiield i o f :resin chemistry :and their specific :compositionsVformfrrorpartof thistinvention. Thezrequirements'thereofe-are:thatftheybe compatible Withisolutions .ofV the explosives, lthatathey gel; atroomtemperature t in a relatively:- short .period .ottime .such-.as aboutfteen min j tutes, `set ypermanently Y: in .about `one thour .and A.thatY.they

impart a viscosity to the solution of the explosive sufficient toprevent the escape of air therefrom and yet be sufficiently fluid forefficient molding and casting. The rate of setting of these resins iscontrolled by the addition thereto of a relatively small proportion(from about 2% to about 4% by weight) of an appropriate curing agent.Such agents have been found to include: benzol peroxide, ditertiarybutylperoxide, cumenehydro peroxide, methylisobutyl ketone peroxide, anddibenzaldeperoxide. The choice of the particular curing agent useddepends upon its compatibility with the solution of the resin and theexplosive and the rate of curing desired. Also an accelerator, such ascobalt naphthanate may be added in a proportional amount of from about2% to about 5% by weight to give additional control on the rate ofgelling and setting of the resin. These curing agents and acceleratorsare herein referred to as setting agents.

Commercially available resins which have been found to be suitable as abond for the foamed explosives of this invention are MR-28C and 29C byMarco Chemicals, Inc., Selectron 5003 and 5016 produced and marketed bythe Pittsburgh Plate Glass Company, Laminac 4128, 4129 and 4116 producedand marketed by the American Cyanamid Company, and Paraplex P-43 by Rohmand Haas Company.

Two methods of the preparation of foamed explosive are preferred by thisinventor. These are (1) the socalled dynamic air-set method, and (2) thechemical blowing method. These methods differ from each other mainly inthe method of introduction of air or gas into the resinous solution ofthe explosive. In the dynamic air-set method (reference being had toFig. 1 of the drawings), a solution of the explosive in styrene, ether,acetone, or a mixture of some o-f these or other solvents is made asindicated yat 10. Only as much explosive may be dissolved as will gointo the solution with or without the application of a moderate heat,and with staying below the decomposition temperature of the explosive. Asolution of a foaming plastic such as a polyester type resin, a curingagent or catalyst and an accelerator is prepared as shown at 12 in theproportionate amounts above indicated. Frorn about to about 30% byvolume of the liquid resin solution is mixed with the solution of theexplosive as shown at 14.

As an example, the diethylene glycol maleate with monomeric styrene ismixed with benzol peroxide and cobalt naphthanate as specifically setforth above. About 20% by volume of this solution is mixed with asaturated solution of TNT dissolved in styrene.

The curing agent and accelerator will cause the resin to gel in about 15minutes and to set permanently in about one hour. The mixture ofsolutions of the explosive and resin is stirred for about 5 minutes asindicated at 15 and allowed to rest for about 5 minutes. Compressed airfrom a source (not shown) is introduced into blowing chamber 18 andthence through forarninous member 20 which may be a glass frit or metalscreen of a mesh in the range of from 75 to 300 and through the mixtureat 14 for about 3 minutes which will foam the said mixture. The foamedmixture is then poured into molds or other containers within theremaining 2 minutes of the 15 at which time the foamed explosive gels orsets up and in one hour becomes a hard cellular mass. By a propercontrol of the viscosity of the mixture, above referred to, air bubblesdo not appreciably escape therefrom after the completion of the blow orduring the period that the `mixture is in the mold prior to gelation.

There is therefore no collapsing of the foamed structure in the mold.

In the chemical blowing process the explosive is dispersed in a suitablesolvent such as acetone or styrene as indicated at 24 in Fig. 2 toobtain .a saturated or highly viscous solution. A solution is preparedby the addition of a curing agent and an accelerator to a foamingplastic in the proportionate amounts above indicated and as shown at 26.The foaming plastic may be a polyester type resin as above described yorother foaming plastics set forth below. In either case they are adjustedto gel in about fifteen minutes and to set in about one hour as in theprocess above described. The solutions of the explosive and the resinare conducted into mixing chamber 28, the solution of the resin beingadded in the proportion by volume of from 10% to 30%. In this chamberthere is added to the mixture from 10% to 30% by volume of a chemicalblowing agent such as diazoaminobenzene or toluene diisocyanate. Themixture is stirred, as indicated at 30 for from five to ten minutes andis then poured or cast into molds as indicated at 32. T he molds arethen heated as indicated at 33 to :a temperature of about C. but notabove decomposition temperature of the explosive at which temperaturethe blowing agent evolves a relatively large volume of gas which causesthe mass to expand forming a cellular structure.

The range in composition, on a percentage weight basis at varioustemperatures of formation, of the foamed explosives of this invention isgiven in the following table:

Percent Percent Percent C. Solvent Range in Explosive Range in Range inTemp. Comp. Comp. Comp.

of Resin acetone 10 T. N. T. 80-(20 10-30 40 T. N. T. 50-30 10-30 30 T.N. T. 60-40 10-30 5-10 T. N. T. 85-00 10-30 5-10 T. N. T. 85-60 10-305-10 T. N. IT. 85-00 l0-30 5 T. N. T. 85435 l0-30 70 PETN 25 5 50 IETN40 10 60 PETN 30 10 25 cyclohexanone 78 RDX l2 10 60 acetone 67 RDX 1815 cyclohexanone. 60 RDX 25 i5 .do 78 HEX-1&2 12 l0 60 acetone. 67HEX-1&2 18 l5 97 cyclohexanone. 60 HEX-1&2 25 15 Other examples usingdifferent foaming plastics are set forth below and it will be understoodby a chemist familiar with the art that such foaming plastics arecapable of use with the dynamic air-set method as well as the chemicalblowing method.

A chemically blown foamed explosive can be prepared by using toluenediisocyanate and alkyd resins to produce a composition referred to inthe art as polyurethane foam resins. Carbon dioxide is liberated in thereaction to cause the plastic to foam and thus, in effect, theingredients act as their own blowing agents.

For purposes of this invention an alkyd resin having followingcomposition is prepared:

7.6 parts by weight glycerol 5.0 parts by weight adipic acid 1.0 part byweight phthalic anhydride These ingredients are refluxed in a glasslined container in an atmosphere of carbon dioxide and at a temperatureof about 165 C. until an acid number of about 55 and hydroxyl number ofabout 415 are reached. The alkyd resin thus formed is then cooled toroom temperature for further use as described below.

Ratios of explosive to resin by weight range from 10% resin to 90%explosive to 50% resin and 50% explosive. Optimum results are obtainedwhere 10 to 30% of resin is used with 90 to 70% of explosive. Thefollowing composition is prepared in the following manner to produce apolyurethane explosive foam:

(A) 150 parts by weight of alkyd resin as prepared above.

(B) 1350 parts by weight of TNT contained in warm acetone (about 30 C.).

(C) parts by weight 2-4 M-toluene diisocyanate.

(D) 58 parts by weight of water.

Ingredients. (A) and.(B) areiirst mixediin azmechani.-A cal mixer suchasea `l-Iobartofsuitable capacity.v Then ingredient (C) ismixedftherewith followedlby'ingredient (D) which'is mixedtherewith orstirredrfor. about 20 minutes.`

This mixture is -then poured into a suitable metal mold calculated toproduce. the desired' density'which infthis case is about l pounds percubic foot. The closed-mold containing the mixture is then placed in ahot-air` oven at about 73 C. for about'one` hou-r afterwhichthe mold isremoved fromtthe hot oven andcooled to room temperature andtheexplosiveTNT foam` is.` removed therefrom.

Another example of a manner of practisingL the invention, which in this`case utilizes a polyvinyl chloride resin with acopolymerofvinyl'chloride and vinyl acetate, follows:

About 100 partsof a polymerized material consisting of about 85% byweight 'of .polyvinyl chloride and yabout byV weightof copolymersAofvinyl chloride and vinyl acetate are mixed in aHobart-mixerwithaboutf80 parts of tricresylphosphate (plasticizer) until thepolyrneris thoroughly dispersed. Aboutt` parts of` P..Poxybis benzene sulfonylhydroxidel (chemical blowing.- agent) is then added and mixedthoroughly. (Diazoaminohenzene or 40% dinitrosopentamethylenetriamine'mayy also be used as chemicalvblowingragentsi)About 3 partslof lead stearate (stabilizer) is also added and'mi'xedthoroughly.

About 80 parts by` weight ofTNT inxatne stateof divison such as willpass through a Standard Sieve No.

50 or 100 (as dened by theAmericanz Society for Testing MaterialsStandards) visth'enadded to the above composition and the mixtureworked-to'. a uniform consistency with astil blade mechanical mixer.About 10% by Weight of the combined'ingredientsl of acetonev isv thenadded slowly and the mass mixed .to uniform consistency.

A suitable charge or volume' of 'this product is placed in a steel moldof tdesired shape.4 Such anzexamplefwould be a mold6. x 6 x 1/2 ofheavyvsteel wall construc-V tion as established inthe art or industry forprocessing. these products. The mold cavity is completelyiilled, and thechargedmold` placedV in` between press'platens at a temperature of about160 C. The: press is then closed and about 5000'p. s. i.' pressureappliedtov the mold and held for about 20 minutes at this temperature.After this time the pressure is reducedto atmospheric and the moldremovedfrom the press. The mold is opened and the molded piece isremoved. It isthen placed in a-hot air oven or chamberat about 120 C.for about 60 minutes when the piece willthen grow or' expand to aboutdouble its volume producing a density between 4 and 7 pounds per cubicfoot. The density canl be considerably changed by varying the chargeinto Vthe mold and the weight of explosive incorporatedinto the mold.

An epoxy resin can be used in carrying out the invention in amanner'such as shown by the-specific example below.

About 110 parts of a diphenol suchv as bisphenol Av is dissolved in 80partsthereofof a 20% water solution of sodium hydroxide. About 188 partsof epichlorhydrin is slowly added to the mixture at about 75 C. overapproximately a 30 minute period. The resulting resin melts at about 65C.

Explosive foam mixture is prepared using the following ingredients:

Epoxy resin as above-98.0 parts.

Ammonium bicarbonate (blowing agent)-10.0 parts. Diglycol laurate S(wetting agent)-3.S parts. Piperidine (curing agent)-2.0 parts.

TNT-400.0 parts.

Epoxy resin as above is heated to the liquid stage at about 75 C. Theammonium. bicarbonate previously dispersedin .diglycol laurateS is .thenadded and stirred thoroughly. TheTNTisthen added and stirred, fol# lowedby thepiperidinewhich is then added'andmixed for about 5 minutes.Theliquid phase life at this stage is` limited to ab0ut.30..minutes;otherwise, polymerization or solidiication sets in. The mixture is thentransferred to a heated metal mold or box held at about 75 C.t for about2V hoursV when the explosive foam is made. The

explosivecompletely lls the container. Of coursethe explosive foammixtures may also be made from nitrocellulose, pentaerythritol, amdcyclo trimethylenetrinitramine. Thedensity of the explosive foam iiscontrolled by varying. the. percentage of explosive going into thecomposition and the weight .of -mix goinginto the heated mold cavity vorbox as describedabove.

This particularexplosive foam composition may also be cured using otheramine reagents such as diamines, triamines orquaternary amines such as,diethylenetrif amine: Vand triethylenetetramine. Commercial resins suchas Shell Chemical Company Epon resins such as Epon 834, Epon-8643 and.Epon 1001" andmixtures of these various resins may also be used.. Cureor harden-V ing-is accomplished by using any one of the amines statedabove.

Referring further tothe drawings,l in Fig. 3 a conventional'oating mineisy shown diagrammatically. and generally at 40. The mine comprisesametallic case 42, Contact elements 44 which are in electric Vcircuits 46with the detonating or exploding device 48. This exploding devicedetonates the charge of high explosive 50- when any one of theelementstd is` actuated by contact Awith an object in the water.Theinterior volume ofthis type of mine is comprisedofabout 50% Aairspace. as shown at 52.

In Fig. 4 the air space of the mine-.shown in Fig. 3 is -lledwith thefoamedV explosive of this inventiontas shown at 54 which. has been curedand set in. place. This foamedor cellular explosive notonly gives anadditive effecttothebrisance? of the high-explosive, but in the event ofleakage through metallic shell 42.due.to erosion or corrosion thereof,.the buoyancy of themine will be.

mine may-be lled with high density explosive therebyV producing a mineof greatly increased shattering eifect when also considered in the lightof the additive explosive effect'of the cellular explosivecomprising theshell.

Fig.` 6"is a sectional illustrationof a lloating harbor mine showing thearrangement of a metallic casing 60, a high density explosive charge62?.,k detonating or exploder device 64, actuating contact element. 66and foarned explosive of this invention 68y surrounding the high.explosive charge and exploder'device and lling .the

air-.space normally present Within fthe .casing of this type of mine. lnthe event of leakage of water through the casing due to corrosionthereof or otherwise, the foamed explosive prevents loss of buoyancyandthe normally resultant loss of the mine.

Fig. 7 is a sectional-elevational view of a torpedo shown generally at70 in which the foamed explosive 72 of this invention lls the normallypresent air-space within the shell 74. The legends in this ligure arebelieved to be self-explanatory. In this embodiment of the invention,the overall buoyancy of the torpedo is less than that of the torpedohaving the conventional air space. But the total shattering etect of theexplosion is much increased by this additional quantity of foamed forcesthe structure.

high explosive. In charging this cellular explosive into this air spacein the torpedo, the foarned explosive is poured into this spaceimmediately prior to the gelling thereof. The space is completely filledand upon the curing and setting of the resin component the cellularexplosive becomes rigid and reinforces the sidewalls of the shell.

Figs. 8 and 9 show the application of the foamed high explosive of thisinvention to the structure of an electronically controlled homing vesselin Sectional-elevational views. Here the double walled hull 90 is shownprovided with radio control 92 for motor drive mechanism 94. Highdensity high explosive 96 substantially fills the interior of hull 90surrounding the exploder device 98. The detonating contact element isshown at 99. The space within the double wall structure of the hull istilled with the foamed high explosive of this invention as shown at 100.As in the case of the torpedo above-described, the foamed explosive ispoured into this hull wall space immediately prior to the gelling andafter setting the foamed cellular explosive mechanically rein- Theadvantage of this type of construction of these homing vessels is thatthe shattering effect of the explosion is greatly increased and that inthe event of leakage through the outer wall of the hull due to corrosionor to any other cause the buoyancy of the vessel is maintained.

It should be understood, of course, that the foregoing disclosurerelates to only preferred embodiments of the invention and that it isintended to cover all changes and modifications of the examples hereinchosen for the purposes of the disclosure, which do not constitutedepartures from the spirit and scope of the invention as set forth inthe appended claims.

What is claimed is:

l. The method of making a high explosive which is less dense than watercomprising the steps of dissolving an explosive selected from the groupconsisting of trinitrotoluene, nitrocellulose, pentaerythritol and cyclotrimethylenetrinitramine in from about to about 80% by weight of asolvent selected from the group consisting of styrene, acetone, toluene,benzene and cyclohexanone, adding thereto from about 5 to about 30% byvolume of liquid polyester resin to form a mixture, said resin catalyzedto gel in about fifteen minutes and to set permanently in about onehour, stirring said mixture for about tive minutes for homogenization,allowing said stirred mixture to rest for about tive minutes,introducing air under pressure for about three minutes in relativelyfine streams into the mass of said mixture to cause said mixture toexpand into a foam structure and pouring the said formed mixture into amolding space wherein said foamed mixture gels and sets permanently toform an explosive of a high degree of cellularity.

2. The method of making a high explosive which is less dense than Watercomprising the steps of dissolving an explosive selected from the groupconsisting of trinitrotoluene, nitrocellulose, pentaerythritol and cyclotrimethylenetrinitramine in from about 5 to about 80% by weight of asolvent selected from the group consisting of styrene, acetone, toluene,benzene and cyclohexanone, adding thereto from about 5 to about 30% byvolume of a liquid polyester resin to form a mixture, said resincatalyzed to gel in about fifteen minutes and to set permanently inabout one hour, adding to said mixture from about 10 to about 30% byvolume of chemical blowing agent selected from the group consisting ofdiazoaminobenzene, and toluene di-isocyanate, stirring said mixture forfrom five to ten minutes for homogenization thereof, pouring saidhomogenized mixture into a mold and heating said molds to about C. butnot above decomposition temperature of the explosive whereupon saidchemical blowing agent decomposes with the liberation of a relativelylarge volume of gas in relatively small bubble form within the mass ofsaid mixture thereby causing said mass to expand to form a foamystructure thereof which immediately gels and sets as a rigid cellularexplosive mass of relatively high strength and toughness.

3. The method of making a foamed explosive of low density comprising thesteps of dissolving an explosive selected from the group consisting oftrinitrotoluene, nitrocellulose, pentaerythritol and cyclotrimethylenetrinitramine in a suitable solvent to make a concentratedsolution, mixing this solution with about 5 to about 50% of a foamingplastic in the liquid state to which has been added a suitable settingagent, introducing air into the mixture under pressure in relativelyfine streams to cause said mixture to expand into a cellular structureand permit said cellular structure to set for a suicient time tosolidify as a foamed explosive.

4. The method as defined in claim 3 where the foaming plastic is apolyester bonding resin.

5. The method as defined in claim 3 where the foaming plastic is apolyurethane resin.

6. The method as defined in claim 3 where the foaming plastic is anepoxy resin.

7. The method as defined in claim 3 where the foaming plastic is apolyvinyl chloride with vinyl chlorideacetate copolymer resin.

8. The method of making a foamed explosive comprising the steps ofdissolving an explosive from the group consisting of trinitrotoluene,nitrocellulose, pentaerythritol and cyclo trimethylenetrinitramine in asuitable solvent tovmake a concentrated solution, mixing this solutionwith about 5 to about 50% of a foaming plastic in the liquid state towhich has been added a suitable setting agent, having a suitablechemical blowing agent into the resultant batch, and heating said batchto a temperature below the decomposition temperature of the explosiveand high enough to cause said chemical blowing agent to decompose andliberate gas whereby the batch is caused to expand to produce a cellularstructure which sets to a solid foamed explosive.

9. The method as defined in claim 8 where the foaming plastic is apolyester bonding resin.

10. The method as defined in claim 8 where the foaming plastic is apolyurethane resin.

ll. The method as defined in claim 8 where the foaming plastic is anepoxy resin.

12. The method as defined in claim 8 where the foaming plastic is apolyvinyl chloride with vinyl chlorideacetate copolymer resin.

No references cited.

1. THE METHOD OF MAKING A HIGH EXPLOSIVE WHICH IS LESS DENSE THAN WATERCOMPRISING THE STEPS OF DISSOLVING AN EXPLOSIVE SELECTED FROM THE GROUPCONSISTING OF TRINITROTOLUENE, NITROCELLULOSE, PENTAERYTHRITOL AND CYCLOTRIMETHYLENETRINITRAMINE IN FROM ABOUT 5 TO ABOUT 80% BY WEIGHT OF ASOLVENT SELECTED FROM THE GROUP CONSISTING OF STYRENE, ACETONE, TOLUENE,BENZENE AND CYCLOHEXANONE, ADDING THERETO FROM ABOUT 5 TO ABOUT 30% BYVOLUME OF LIQUID POLYESTER RESIN TO FORM A MIXTURE, SAID RESIN CATALYZEDTO GEL IN ABOUT FIFTEEN MINUTES AND TO SET PERMANENTLY IN ABOUT ONEHOUR, STIRRING SAID MIXTURE FOR ABOUT FIVE MINUTES FOR HOMOGENIZATION,ALLOWING SAID STIRRED MIXTURES TO REST FOR ABOUT FIVE MINUTES,INTRODUCING AIR UNDER PRESSURE FOR ABOUT THREE MINUTES IN RELATIVELYFINE STREAMS INTO THE MASS OF SAID MIXTURE TO CAUSE SAID MIXTURE TOEXPAND INTO A FOAM STRUCTURE AND POURING THE SAID FORMED MIXTURE INTO AMOLDING SPACE WHEREIN SAID FOAMED MIXTURE GELS AND SETS PERMANENTLY TOFORM AN EXPLOSIVE OF A HIGH DEGREE OF CELLULARITY.